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From the Labs: Biotechnology

New publications, experiments and breakthroughs in biotechnology–and what they mean.
August 19, 2008

Magnetic Genes
Genetically ­engineered cells make their own nano magnets, providing clear MRI images

This MRI of a mouse brain clearly shows a dark circle (arrow) of magnetic cells. The cells, genetically engineered to produce magnetic particles and then injected into the brain, could provide a new approach to imaging.

Source: “MagA is sufficient for producing magnetic nanoparticles in mammalian cells, making it an MRI reporter”
Xiaoping P. Hu and Anthony W. S. Chan
Magnetic Resonance in Medicine
59: 1225-1231

Results: Scientists genetically engineered mammalian cells to produce magnetic particles three to five nanometers in diameter. The particles can be detected with magnetic resonance imaging (MRI), which could give scientists a novel way to track cells in the body.

Why it matters: Scientists typically use fluorescent markers to track specific cell types. But fluorescent signals can’t travel very far through animal tissue, so the approach is of limited use in live studies. Cellular labels detectable with MRI, which can see deep into the body, could allow scientists to observe a range of biological processes as they unfold in live animals.

Methods: From a pond-­dwelling bacterium, scientists isolated a gene for producing magnetic particles, which the bacterium uses like a compass. They inserted the gene into human cells and injected the cells into the brains of live mice. The mouse cells began to produce their own magnetic particles and could be seen clearly with MRI.

Next steps: The researchers will further assess how the nanoparticles could be used with MRI by better characterizing them and measuring their effect on cells–determining, for ­example, whether they are toxic or whether they alter cellular functions in living animals.

Genetically Prescribed Vitamins
Newly discovered genetic variations could predict who needs more folic acid

Source: “The prevalence of folate-remedial MTHFR enzyme variants in humans”
Nick Marini et al.
Proceedings of the National Academy of Sciences
105: 8055-8060

Results: Scientists at the University of California, Berkeley, identified several new variations in the gene for methylenetetrahydrofolate reductase (MTHFR), an enzyme that converts the B vitamin folate (called folic acid in supplements) from one form into another. They found that some variants of the enzyme need more folate to work effectively, a finding that could have implications for human nutrition.

Why it matters: Scientists hope that this type of research will eventually pave the way for individually tailored doses of vitamins. In particular, the work may help suggest who needs to take more folic acid to prevent ailments such as birth defects and possibly heart disease, which have been linked to malfunction of the MTHFR enzyme.

Methods: Researchers sequenced the MTHFR gene in 564 people of different ethnicities. Then they added the human gene sequences to yeast cells, which were engineered so that their growth rate depended on how well the enzyme was working. By feeding the yeast varying amounts of folate, the scientists could determine which of the genetic variants needed more of the vitamin to function properly.

Next steps: An ongoing human study performed in collaboration with the Children’s Hospital Oakland Research Institute and the Joint Genome Institute in Walnut Creek, CA, should provide more data on the enzyme’s role in birth defects. Scientists will sequence the gene in 250 normal children and 250 children with neural-tube defects to see whether the poorly functioning variants appear more often in the latter.

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